This invention relates to bus controller cards, and more particularly to preventing conflicts between bus controller cards.
Mass storage units are commonly used in applications where large amounts of data need to be stored. Typically, such mass storage units each contain a number of disk drives connected via a bus, such as a Small Computer System Interface (SCSI) bus that is standard in the art. Such mass storage units typically include one or more bus controller cards to control the bus. Those one or more cards generally connect to a backplane on which the bus is implemented. Bus controller cards may be configured via switches, jumpers or other physical controls on the cards that allow a user to reconfigure the cards as needed. Bus addressing and termination of each card is typically controller via such switches.
The backplane may include slots for two or more bus controller cards. However, the use of two or more bus controller cards can introduce compatibility and data corruption problems. For example, where two bus controller cards of the same type are used, and the switches on each card set bus addressing and termination in an incompatible manner, undesirable effects may occur, such as corruption or loss of data sent across the bus, and bus lockup. As another example, the backplane may be capable of receiving two different and incompatible bus controller cards, for purposes of backward compatibility or the like. If those two incompatible cards are inadvertently inserted at the same time, problems such as data loss or corruption, or bus lockup, may occur.
A backplane having a bus may receive two bus controller cards, of the same type or of different types, and one of those cards may be disconnected if incompatible with the other to prevent data corruption on the bus.
In one aspect of the invention, a backplane having a bus is adapted to receive two bus controller cards of the same model. One of the bus controller cards is a master card and the other is a servant card. Each of the bus controller cards has a bank of DIP switches that may be set to compatible positions. The positions of the DIP switches on the two bus controller cards are compared, and the servant card is disconnected if its DIP switches are not set to positions compatible with those of the master card, thereby preventing corruption or loss of data traveling over the bus.
In another aspect of the invention, a backplane having a bus is adapted to receive different models of bus controller cards. Where two different models of bus controller cards are present on the backplane at the same time, one of the cards is not connected to the bus in order to prevent corruption or loss of data traveling over the bus.